1. Field of the Invention
The present invention relates to an apparatus for joining or connecting sheet metal pieces, and in particular, to a tool set to be mounted in a press.
2. Description of the Background Art
U.S. Pat. Nos. 4,614,017, 4,658,502, 4,584,753, and pending U.S. patent application Ser. Nos. 07/314,007 and 07/324,825 disclose devices of the general nature to which the tool set of the present invention belongs, and the disclosures thereof are incorporated herein by reference. Briefly, a male die is mounted in a press ram and a female die is mounted in a press frame. The female die defines a cavity into which a section of sheets disposed between the dies is deformed by the male die. In a first phase of deformation, the male die performs an embossing operation between forming members of the female die and, in a second phase, subjects the embossed material to pressure between the male die and an anvil of the female die so that the embossed material flows laterally to result in a rivet like connection or joint as the forming members, during the second phase, yield laterally. Only one single press stroke is necessary to complete the connection.
The female die need not have laterally yielding forming members if a double stroke press is used, as disclosed in U.S. Pat. No. 3,726,000. The forming members of the female die remain stationary but its anvil is displaced against the male die so as to perform the cold flux deformation. It is generally assumed that connections so made may be more rigid than those of the firstly described process.
It is an object of the present invention to provide a tool set which allows the formation of very rigid connections of the secondly mentioned type but which does not need a double stroke press.